Android的 - 淡出在画布上的位图图像 [英] Android - Fade out bitmap image on canvas
问题描述
我绘制位图缩放到画布上,并想淡出我的形象了,在指定的时间。
I am drawing a scaled bitmap onto a canvas and would like to fade my image out at a specified time.
基本上,当我的人物形象越过画布的某一部分,我需要的人物形象慢慢消逝(3秒),之前的页面会自动重新定向到下一个Java类。
Basically, when my character image goes over a certain section of the canvas, I require the character image to slowly fade away (3 seconds), before the page automatically re-directs to the next java class.
目前,我的形象只是重定向到新的Java类,请参见下面的一些code到我如何创建我的形象。
Currently, my image simply redirects to the new java class, please see below some code to how I am creating my image.
Resources res = getResources();
float px = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, 20, res.getDisplayMetrics());
imgSpacing = (int) px / 2;
int size = (int) ((PhoneWidth / 5) - px);
chrImg = BitmapFactory.decodeResource(getResources(), R.drawable.character);
chrImg = Bitmap.createScaledBitmap(chrImg, size, size, true);
然后在画布上的OnDraw:
Then within the canvas onDraw:
if(indexX == mazeFinishX && indexY == mazeFinishY)
{
canvas.drawBitmap(finish, j * totalCellWidth, i * totalCellHeight, null);
// As soon as the character moves over this square they are automatically re-directed to new page
// This is where I want to fade the character image out before the re-direct
}
我在网上看了看,但不能完全解决如何让衰落的工作为我绘制的图像从我的游戏资源,可绘制文件夹中取出。谢谢
I have looked online, however cannot quite work out how to get the fading to work for my drawable image fetched from my games resources drawable folder. Thanks
推荐答案
如果你认为有,你会想改变动画渐变的道路,如缩放和/或旋转的可能,那么你应该用动画去XML。
If you think there's a possibility you will want to change the fade animation down the road, such as scaling and/or rotating, then you should go with an animation XML.
但只是一个快速的位图褪色,可以反复延迟后无效的消息。你可能希望你的无效面积限制只在您的性格位图:
But for just a quick bitmap fade, you can repeatedly post delayed invalidation messages. You probably want to limit your invalidated area to just where your character bitmap is:
private static final int FADE_MILLISECONDS = 3000; // 3 second fade effect
private static final int FADE_STEP = 120; // 120ms refresh
// Calculate our alpha step from our fade parameters
private static final int ALPHA_STEP = 255 / (FADE_MILLISECONDS / FADE_STEP);
// Initializes the alpha to 255
private Paint alphaPaint = new Paint();
// Need to keep track of the current alpha value
private int currentAlpha = 255;
@Override
protected void onDraw(Canvas canvas) {
...
if(indexX == mazeFinishX && indexY == mazeFinishY) {
// Drawing your wormhole?
int x = j * totalCellWidth;
int y = i * totalCellHeight;
canvas.drawBitmap(finish, x, y, null);
if (currentAlpha > 0) {
// Draw your character at the current alpha value
canvas.drawBitmap(chrImg, x, y, alphaPaint);
// Update your alpha by a step
alphaPaint.setAlpha(currentAlpha);
currentAlpha -= ALPHA_STEP;
// Assuming you hold on to the size from your createScaledBitmap call
postInvalidateDelayed(FADE_STEP, x, y, x + size, y + size);
} else {
// No character draw, just reset your alpha paint
currentAlpha = 255;
alphaPaint.setAlpha(currentAlpha);
// Now do your redirect
}
}
...
}
我建议你把常量FADE_MILLISECONDS和FADE_STEP到RES / integers.xml只是让他们没有硬codeD。
I'd recommend putting the constants FADE_MILLISECONDS and FADE_STEP into res/integers.xml just so they aren't hard-coded.
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